WASHINGTON (Reuters) – The U.S. Supreme Court (news – web sites) let stand on Tuesday a ruling that the government cannot revoke the federal prescription licenses of doctors who recommend medical marijuana to sick patients.

Without any comment, the justices rejected a Bush administration appeal of the ruling that bars the government from punishing and from even investigating a doctor’s conduct because of a recommendation that a patient use marijuana

The federal government has classified marijuana as a controlled substance, an illegal drug, saying it has "a high potential for abuse," "no currently accepted medical use" and is unsafe even when used under medical supervision.

A U.S. appeals court in San Francisco ruled the federal government’s policy against doctors who recommend marijuana violated constitutional free-speech rights of physicians and patients.

The case began after California voters in 1996 adopted Proposition 215, which makes it legal for seriously ill patients to grow and possess marijuana for medical use when a doctor recommends it.

The Clinton administration threatened to revoke the licenses of physicians who recommended marijuana as a medical treatment, a policy the Bush administration has continued and defended.

In 1997, a number of physicians and patients sued in federal court in California.

The appeals court upheld a federal judge’s injunction that bars the U.S. Drug Enforcement Administration from revoking a physician’s registration to prescribe federally regulated narcotics. The agency also was barred from even beginning an investigation of any doctor who recommended marijuana.

Solicitor General Theodore Olson of the Justice Department (news – web sites) appealed to the Supreme Court and said the decision impaired the government’s power "to enforce the law in an area vital to the public health and safety."

He said the appeals court decision imposed "sweeping and unprecedented restrictions on the government’s ability even to investigate possible violations of the law."

Lawyers from the American Civil Liberties Union, which helped represent those challenging the policy, opposed the appeal. They called the government policy censorship of speech covered by the physician-patient relationship.

"What’s at issue is the ability of doctors to speak openly and honestly with their patients about marijuana as a viable therapy option," said Graham Boyd, director of the ACLU’s Drug Policy Litigation Project.